CHAPTER 26. DIARRHEA
Debra E. Heidrich
DEFINITION AND INCIDENCE
Diarrhea is defined as an increase in stool volume and liquidity, resulting in the passage of three or more loose or unformed stools per day (Carpenito, 2000; Rogers, 2005; Sykes, 2003). This symptom, however, is somewhat subjective: some may report three soft stools in a day as diarrhea, but others may report only stools that are liquid and occur in large volume. Diarrhea is often associated with abdominal cramping and rectal urgency (Carpenito, 2000; Levy, 1991). Uncontrolled diarrhea can lead to fluid and electrolyte imbalances, resulting in lethargy, weakness, and orthostatic hypotension. In addition, persistent diarrhea may lead to malnutrition, impaired skin integrity, altered sleeping patterns, social isolation, anxiety, and self-concept disturbances.
Approximately 7% to 10% of persons with advanced cancer report diarrhea (Sykes, 2003; Waller & Caroline, 2000), and 50% or more of those with human immunodeficiency virus (HIV) disease may experience this symptom (Cohen, West, & Bini, 2001; Sykes, 2003). The number of acquired immunodeficiency virus (AIDS) patients admitted to the hospital for uncontrolled diarrhea has decreased with the use of highly active antiretroviral therapy. A review of data from the state of New York in 1998 revealed that of the 15,000 persons with AIDS admitted to hospitals, 2.8% had a diarrheal diagnosis (Anastasi & Capili, 2000). This study did not indicate the number of persons with AIDS who experience diarrhea that is not severe enough to warrant hospitalization. Even mild to moderate diarrhea can have debilitating effects. Sanchez, Brooks, Sullivan et al. (2005) reported that although the incidence of bacterial diarrhea in patients with HIV disease decreased over the decade of 1992 to 2002, there is still an increased incidence over the general population and the risk of diarrhea increases with increased severity of HIV disease.
Most diarrhea is acute, lasting only a few days, and is generally due to infection or overuse of laxatives. Diarrhea that lasts longer than 3 weeks is considered chronic and is usually due to organic disease (Sykes, 2003).
ETIOLOGY AND PATHOPHYSIOLOGY
The three most common causes of diarrhea in persons with advanced cancer are laxative overdose, fecal impaction with overflow diarrhea, and partial bowel obstruction (Sykes, 2003; Mercadante, 2002). Other common causes are radiation enteritis, medications, and steatorrhea. In persons with AIDS, infection is often the cause, although the pathogen is not always identifiable.
Any condition that increases secretion within the gastrointestinal (GI) tract, interferes with reabsorption from the GI tract, increases the motility of the GI tract, or causes excretion of mucus, fluids, or blood can cause diarrhea. These correspond with the general mechanisms of diarrhea: secretory, osmotic, hypermotile, and exudative (Lingappa, 2003). Diarrhea in the terminally ill often involves more than one mechanism. The pathophysiological characteristics of these mechanisms are discussed later. Table 26-1 includes many of the conditions that lead to diarrhea in the palliative care setting, the pathophysiological mechanism(s), descriptors that may be helpful in determining the type and cause of this symptom, and suggested interventions.
| Cause | Mechanism(s) | Descriptors | Treatment |
|---|---|---|---|
| Cancer-Related Diarrhea | |||
| Endocrine-producing tumor | Secretory via production or stimulation of secretagogues |
High volume, watery
Associated with abdominal cramping
|
Encourage or replace fluids, as needed
Control diarrhea: antidiarrheals
Inhibit intestinal secretion (if severe): octreotide, clonidine
Treat pain: anticholinergics
|
| Obstruction | Exudative and hypermotility | Alternating constipation and diarrhea, often with mucus and blood; colicky pain |
Reduce inflammation: steroids
Treat pain: anticholinergics
Control diarrhea: cautious use of antidiarrheals
|
| Biliary or pancreatic obstruction | Osmotic due to fat malabsorption | Steatorrhea: large volume, pale, foul odor; feces floats in toilet |
Decrease dietary fat
Treat fat malabsorption: pancreatic enzymes, famotidine
|
| Cancer Treatment–Related Diarrhea | |||
| Chemotherapy | Secretory due to damage to villi, inhibiting absorption; hypermotility due to irritation |
High volume, watery; may be explosive
Associated with colicky pain
|
Encourage or replace fluids, as needed
Slow motility: antidiarrheals
Inhibit intestinal secretion (if severe): octreotide, clonidine
Treat pain: anticholinergics
|
|
Radiation therapy
▪ Acute
|
Secretory (due to inflammation and bile salt malabsorption), osmotic, and hypermotility due to effects of bile salts |
High volume, watery, explosive
Associated with abdominal cramping
Usually self-limiting
|
Encourage or replace fluids, as needed
Treat inflammation: nonsteroidal anti-inflammatory drugs
Absorb bile salts: cholestyramine
Slow motility: antidiarrheals
|
|
Radiation therapy
▪ Chronic (may occur 5 to 15 years after treatment)
|
Ischemic enteritis, ulcerations, or impaired cellular functioning; may be secretory and/or osmotic | Depends on mechanism; generally high volume and watery |
Encourage or replace fluids, as needed
Control diarrhea: antidiarrheals
Absorb bile salts: cholestyramine
|
|
Surgery
▪ Gastrectomy
|
Secretory, osmotic, and hypermotility due to “dumping syndrome” and potential for bile salt malabsorption |
High volume with undigested food
Associated with nausea, vomiting, flatulence, and colicky pain
|
Frequent, small meals
Control diarrhea: antidiarrheals
Bile salt malabsorption: cholestyramine
Treat pain: simethicone for gas pain; anticholinergics for colicky pain
|
|
Surgery
▪ Ileal resection
|
Secretory, osmotic, and hypermotility due to poor reabsorption of bile salts | High volume with undigested food |
Frequent, small meals
Control diarrhea: antidiarrheals
Bile salt malabsorption: Cholestyramine
Treat pain: simethicone for gas pain; anticholinergics for colicky pain
|
|
Surgery
▪ Short bowel syndrome
|
Osmotic due to decreased fluid absorption | Depends on length of bowel resected: loose to watery |
Increase bulk of stool: bulk-forming laxatives
Slow motility: antidiarrheals
|
| Infection-Related Diarrhea | |||
| Noninflammatory infections (e.g., viruses, Escherichia coli, Staphylococcus aureus) | Secretory due to stimulation of secretagogues via endotoxins |
Often self-limiting
Watery, without pus or mucus
Associated with periumbilical cramping, nausea, and vomiting
Temperature normal or slightly elevated
|
If prolonged:
Treat infection, when possible
Encourage or replace fluids, as necessary
Control diarrhea: antidiarrheals, using bismuth subsalicylate (Pepto-Bismol) as first choice, if required
Treat pain: anticholinergics
|
| Inflammatory infections (e.g., Shigella, Salmonella, Campylobacter spp., invasive E. coli) | Secretory |
Loose to watery, often with blood, pus, or mucus
Associated with lower abdominal cramping, rectal urgency, and fever
|
Treat infection, when possible
Encourage or replace fluids, as necessary
Control diarrhea: antidiarrheals
Treat pain: anticholinergics
|
| Cryptosporidiosis | Secretory | High volume, watery, explosive; associated with abdominal cramping, fever, and vomiting |
Treat immunosuppression: antiretroviral therapy
Treat infection: nitazoxamide or paramomycin
Encourage or replace fluids, as necessary
Control diarrhea: antidiarrheals
Treat pain: anticholinergics
|
| Other Treatment-Related Diarrhea | |||
| Overuse of laxatives | Depends on type(s) of laxative; usually osmotic or hypermotility | Frequent, loose stools | Discontinue or decrease dose of laxatives |
| Impaction | Exudative |
Rectal leakage with too much softener; cramping with too much stimulant
Small amounts of dark, mucuslike liquid; rectal pressure
|
Perform disimpaction
Begin or adjust laxative protocol
|
| Enteral supplements or feedings | Osmotic due to hyperosmolality of supplement or due to lactose intolerance |
Large volume and watery
Associated with abdominal cramping, distension, and flatulence
Low stool pH
|
Dilute supplement with water and gradually increase strength
Consider using bulk-forming agents
Evaluate need for lactose-free supplement
|
| Celiac plexus block | Hypermotility due to suppression of sympathetic nervous system |
Moderate to large volume, loose stool
May be self-limiting
|
Slow motility: antidiarrheals; anticholinergics |
| Anxiety | Hypermotility and secretory of lower gastrointestinal tract via parasympathetic stimulation |
Generally moderate to large volume; loose stool
Stool may contain mucus
|
Treat anxiety: address psychosocial concerns;
Teach relaxation techniques;
Evaluate need for anxiolytic
|
| Medication | Often secretory | Secretory is generally large volume; but diarrhea character may vary with offending medication | Stop offending medication, when possible |
Pathophysiological Characteristics of Secretory Diarrhea
The lining of the walls of the small intestine includes small pits, called the crypts of Lieberkühn, that lie between the intestinal villi. The crypts produce the four cell types of villi: enterocytes, goblet cells, enteroendocrine cells, and Paneth cells. The mucus of the goblet cells lubricates and protects the surfaces of the bowel lumen. The enterocytes of the crypts secrete large quantities of water and electrolytes, and those of the villi reabsorb water and electrolytes along with the products of metabolism. The enteroendocrine cells secrete hormones into the bloodstream, and the Paneth cells produce antimicrobial peptides and growth factors (Lingappa, 2003). Active secretion that overwhelms the absorptive processes of the GI tract leads to diarrhea that generally persists with fasting (Mercadante, 2002). Substances that increase bowel secretions (secretagogues) include vasoactive intestinal polypeptide, calcitonin, serotonin, bradykinin, substance P, prostaglandins, and gastrin (Levy, 1991; Lingappa, 2003; Mercadante, 2002). Conditions that lead to the production of one or more of these secretagogues include the following:
▪ Inflammation in the bowel wall causes the release through the cyclooxygenase pathway of prostaglandins, which stimulate bowel secretions. In addition, the inflammation interferes with the absorption process, further contributing to diarrhea (Mercadante, 2002). This is the likely mechanism for the diarrhea associated with acute radiation enteritis, chemotherapy, and infection.
▪ Two infections that lead to significant fluid and electrolyte losses from secretory diarrhea are cryptosporidiosis and pseudomembranous colitis. Cryptosporidium sp., a common cause of diarrhea in the AIDS population, attaches to the intestinal epithelium. It damages the enterocytes, leading to impaired absorption and enhanced secretion within the intestinal tract (Rogers, 2005). The diarrhea of cryptosporidiosis is profuse and watery and is associated with abdominal cramping, fever, and vomiting (Woodruff & Glare, 2003). Pseudomembranous colitis is caused by colonization with Clostridium difficile after antibiotic therapy. C. difficile produces toxins that damage the mucosa, leading to a secretory diarrhea (Rogers, 2005). Symptoms begin within 1 week to 1 month of starting antibiotic therapy.
▪ Certain tumors, including small-cell lung cancer, ganglioneuroma, pheochromocytoma, carcinoma of thyroid, malignant carcinoids, and gastrinomas, produce one or more of these secretagogue substances (Mercadante, 2002).
▪ The inability to reabsorb bile acids from the small intestine leads to diarrhea via the secretory effect of these substances on the mucosa of the colon and their osmotic effect in the colon. The result is diarrhea that is watery and explosive (Mercadante, 2002; Sykes, 2003). Ileal resection, gastrectomy with vagotomy, and postirradiation enteritis may interfere with bile acid reabsorption.
▪ Some medications, such as caffeine, theophylline, antacids, some antibiotics, and poorly absorbable osmotic laxatives, also cause secretory diarrheas via direct simulation of secretions or secondary to irritation of the epithelial cells (Mercadante, 2002).
Pathophysiological Characteristics of Osmotic Diarrhea
The small bowel is highly permeable to sodium and water transport but not to solute. When large amounts of nonabsorbable sugar (e.g., lactulose and sorbitol) are ingested, the ability of the GI tract to compensate may be overwhelmed, resulting in diarrhea from the osmosis of fluid into the lumen. The diarrhea due to carbohydrate malabsorption is characterized by a low pH, high content of carbohydrates, high stool osmolality, and flatulence. Other substances that cause osmotic diarrhea are magnesium, sulfate, and poorly absorbed salts, including bile salts. The pH of diarrhea caused by one of these latter substances is usually normal (Mercadante, 2002).
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